Some problems occurred with time-out of the grism wheels which is
somehow related to the balance of this wheel, though it is not clear
how this can cause the problem. Later models of FOSC's have a
different design in the way the wheels are driven and they do not seem
to have this problem. It was checked with Niels Michaelsen in
Copenhagen what the difference are, but it turns-out that modifying
the current wheel to a similar design would be a major operation.